A country sewage treatment plant (rural area) was monitored in 2002-2005 to follow the raw and treated sewage compn. both in rainy days (12 samples) and during rainless weather (12 samples). The samples collected were analyzed for BOD5 and COD as well as suspensions, N and P contents. During the rainy days, the quality of the treated sewage was better than during the rainless weather but the total pollutant loads in the outflow were much higher during the rainy days (except for P content). The efficiency of the sewage treatment plant was decreased in the rainy days by the increased amount of dild. sewage to be processed.